It is well known to rotatably support a filmstrip on a spool within a film cassette. In some such arrangements, the end of the filmstrip adjacent the spool is not secured thereto and there is a risk that the filmstrip will inadvertently become detached from the spool and hence be wholly withdrawn from the cassette during its exposure. One such arrangement is described in U.S. Pat. No. 4,145,133.
There are other arrangements which overcome this problem by attaching the trailing edge of the filmstrip to the spool. These arrangements prevent the filmstrip being fully extracted from the cassette during exposure, but necessitate the use of a cutter to detach the filmstrip from the spool prior to processing.
U.S. Pat. No. 5,054,710 discloses a spool for a camera on to which a filmstrip is to be wound during exposure. The spool includes a shaft having a slit formed therein. A protrusion is located in the slit to engage a perforation in the leading edge of the filmstrip, the filmstrip being wound on to the spool as it is exposed in the camera. When the filmstrip is fully exposed, it is unwound from this spool back into its cassette. The leading edge of the filmstrip slips out of the slit as the wall of the perforation engaging the protrusion slides down an angled wall thereof to release the filmstrip from the spool.
U.S. Pat. No. 4,334,750 discloses an arrangement for a spool in a film cassette which allows the trailing edge of the filmstrip to be released. The arrangement comprises a hollow spool having a slot formed in its wall. A retaining member is located within the hollow spool and carries a protrusion for engaging a perforation in the trailing edge of the filmstrip to retain it in the slot. When it is desired to release the filmstrip from the spool, the retaining member is pushed inwardly with respect to the spool so that the protrusion is forced out of the slot thereby releasing the perforation and the trailing edge. Once pushed in, the retaining member cannot be withdrawn from the spool.